The present invention relates generally to filter devices for placement in a blood vessel to capture embolic material, and more particularly to a catheter system having an associated filter for percutaneous placement in an aorta to entrap embolic material from the aorta and heart during cardiac surgery.
Stroke has become a major source of morbidity following coronary artery bypass and other cardiovascular surgeries, including valvular repair, septal defect repair, removal of atrial myxoma, aneurysm repair, and myocardial drilling. Classic factors associated with an increased post-operative stroke rate are advanced age, severe left ventricular dysfunction, long standing diabetes, protracted cardiopulmonary bypass time, severe perioperative hypotension, history of previous stroke, and bilateral carotid disease. Possible mechanisms of perioperative stroke include a reduction in cerebral blood flow through a stenotic extracranial or intracranial vessel, embolization of atherosclerotic debris from an ulcerated carotid artery plaque or aortic plaque, embolization of post-infarction left ventricular mural thrombus or atrial thrombus, and embolization of air inadequately evacuated from the heart or aorta. In valvular repair surgery, manipulation of the heavily calcific aortic or mitral valve may result in calcium dislodgment in the left coronary artery or left ventricle, with subsequent embolization. Although atheromatous debris most frequently embolizes to the brain, other affected body sites include the spleen, kidney, pancreas, and gastrointestinal tract. Embolization of these peripheral organs can lead to tissue ischemia or death.
In addition to stroke, other factors, e.g., chest wall trauma, contributing to morbidity in cardiac surgeries often arise from the use of cardiopulmonary bypass for circulatory support and median sternotomy. Minimally invasive procedures using beating-heart and port-access approach have been developed to achieve aortic occlusion, cardioplegia delivery, and left ventricular decompression to allow coronary revascularization and other cardiac procedures to be performed in a less invasive fashion.
A need therefore exists for less invasive devices and methods which facilitate aortic occlusion and/or cardioplegia delivery in cardiac surgeries and provide an arterial filter for reducing a patient""s risk of perioperative stroke.
The present invention provides a percutaneous filtration catheter having the ability to capture emboli, including atheromatous fragments, fat, myocardial tissue debris, and air. The catheter further includes capabilities to provide aortic occlusion and cardioplegia delivery in cardiac surgeries, especially in heart valve repair.
In one embodiment, the catheter comprises an elongate member having proximal and distal ends. The distal end has (1) a balloon occluder which communicates with a lumen carried by the elongate member, and (2) an expandable filter mounted on the elongate member distal to the balloon occluder. The balloon occluder and the expandable filter are operated independently at the proximal end of the elongate member. The expandable filter typically has a proximal edge bonded circumferentially and continuously to the elongate member, and a distal edge which expands radially outward on activation.
In another embodiment, the elongate member has a second lumen for infusing fluid, such as cardioplegia solution. The expandable filter may comprise an expansion frame, which may have an umbrella frame in one embodiment (for construction, see Barbut et al., U.S. Pat. No. 5,769,816, and Ambrisco et al., U.S. Ser. No. 09/070,660, both incorporated herein by reference in their entirety) and an inflation seal in another embodiment (for construction, see Barbut et al., U.S. Pat. No. 5,769,816). Furthermore, in certain embodiments, the expandable filter is operable by manipulating at least one pull string at the proximal end of the elongate member.
The present invention also provides methods for capturing embolic material in cardiac surgeries, thereby protecting a patient from neurologic complication due to embolization. The methods employ a percutaneous filtration catheter having an elongate member with proximal and distal ends, a balloon occluder mounted on the distal end of the elongate member, and an expandable filter mounted on the elongate member distal the balloon occluder. A percutaneous incision in a patient""s peripheral artery, such as a femoral or brachial artery, is made followed by insertion of the elongate member through the incision. In minimally invasive cardiac procedures, the percutaneous filtration catheter can be introduced percutaneously through a peripheral artery, or alternatively, through a minimal access port, often located in a patient""s intercostal space, to the ascending aorta. The distal end of the catheter is then advanced into the ascending aorta. The filter is expanded and positioned above the aortic valve to entrap embolic material from flowing downstream to peripheral organs. The balloon occluder is inflated to provide circulatory isolation of the heart and coronary blood vessels from the peripheral vascular system. In the embodiment which includes a second lumen, the second lumen can be used to (1) deliver cardioplegia solution upstream to the heart to arrest cardiac function, or (2) to carry a pressure monitor. After cardiac arrest is achieved and cardiopulmonary bypass is initiated for circulatory support, a variety of cardiothoracic surgeries can then be performed, including coronary artery bypass grafting, heart valve repair, septal defect repair, removal of atrial myxoma, aneurysm repair, and myocardial drilling.
It will be understood that are many advantages to using a percutaneous filtration catheter as disclosed herein. For example, the catheter provides (1) a percutaneous access for catheter insertion, obviating the need for an extensive tissue incision, (2) aortic occlusion through inflating a balloon occluder, thereby minimizing damage to the aortic wall and reducing the risk of emboli dislodgment as compared to traditional clamping, (3) a filter which entraps embolic material during cardiac surgery, thereby reducing a patient""s risk of stroke perioperatively, (4) cardioplegia delivery upstream to the heart for cardiac arrest, and (5) access for devices to be introduced through an intercostal incision in minimally invasive cardiac procedures.